It is desirable to use a powertrain mount that has a large deflection to load characteristic that is to say, a soft mount, in order to maximize the vibration absorption properties of the mount. This is particularly the case when there is substantially no load being transmitted via the powertrain mount such as when an engine is idling and a transmission is in neutral.
However, when the powertrain mount is subject to applied load the use of a soft mount will likely permit an unacceptably high level of displacement of the powertrain component to occur. This is problematic in that it can result in high loads being transferred to associated components such as an exhaust system or require a large clearance to be provided between the engine or transmission and the adjacent parts of the motor vehicle. It will be appreciated that in a modern motor vehicle there is considerable pressure to minimize package space and so the need to provide a large clearance between the engine and/or transmission and adjacent parts of the motor vehicle is undesirable.
Example embodiments of the present application may provide a powertrain mount assembly that permits the use of a relatively soft mount for low load conditions while providing sufficient restraint under load to allow displacement to be minimized.
According to a first aspect of the disclosure there is provided a powertrain mount assembly for connecting a powertrain component to a structural part of a motor vehicle, the assembly comprising a resilient mount for connection to the structural part of the motor vehicle, a connecting arm for connecting the resilient mount to the powertrain component and an actuator to displace the resilient mount relative to the structural part of the motor vehicle and a controller to control the actuator to displace the resilient mount in response to an input indicative of an expected movement of the powertrain component wherein the resilient mount comprises a frame, first and second resilient members mounted in the frame and interposed between the connecting arm and the frame such that movement of the connecting arm in a first primary direction is resisted by compression of the first resilient member and movement of the connecting arm in a second primary direction that is opposite to the first primary direction is resisted by compression of the second resilient member and, when the input indicates that the powertrain component is expected to be displaced relative to the structural part of the motor vehicle, the controller is arranged to use the actuator to displace the frame of the resilient mount in an opposite direction to the expected movement of the powertrain component so as to produce a pre-load in a respective one of the first and second resilient members of the resilient mount.
The displacement of the resilient mount from its nominal position may be arranged to be proportional to the expected load to be transmitted by the resilient mount.
A fixed support member may be provided for fastening to the structural part of the motor vehicle, the frame of the resilient mount may be moveably connected to the fixed support member and, when the powertrain component is expected to be displaced relative to the structural part of the motor vehicle, the actuator may be arranged to displace the frame of the resilient mount relative to the fixed support member in an opposite direction to the expected movement of the powertrain component.
The frame of the resilient mount may be arranged for sliding attachment directly to the structural part of the motor vehicle and, when the powertrain component is expected to be displaced relative to the structural part of the motor vehicle, the actuator may be arranged to displace the frame of the resilient mount relative to the structural part of the motor vehicle in an opposite direction to the expected movement of the powertrain component.
The powertrain component may be one of an engine and a transmission.
The resilient mount may comprise a frame, first and second resilient members mounted in the frame and interposed between the connecting arm and the frame such that movement of the connecting arm in a first primary direction is resisted by compression of the first resilient member and movement of the connecting arm in a second primary direction that is opposite to the first primary direction is resisted by compression of the second resilient member.
The resilient mount may further comprise one or more additional resilient members arranged to resist movement of the connecting arm in one or more direction other than the first and second primary directions.
The resilient members may be formed as a single unitary component.
The first and second primary directions may be directions the powertrain component is expected to be displaced relative to the structural part of the motor vehicle when subject to variations in applied load.
According to a second aspect of the disclosure there is provided a motor vehicle having a body structure, an engine driving a transmission, a powertrain mount constructed in accordance with said first aspect of the disclosure connecting one of the engine and the transmission to a structural member forming part of the body structure of the motor vehicle and the controller controls the actuator to displace the resilient mount in response to the input indicative of the expected movement of one of the engine and the transmission.
The input may be a signal indicative that a state of the transmission is changing from a neutral state to a drive state.
The drive state of the transmission may be a forward drive state.
Alternatively, the drive state of the transmission may be a rear drive state.
The input may be a signal indicative that a torque demand for the engine is to be rapidly increased.
Alternatively, the input may be a signal indicative that a torque demand for the engine is to be rapidly reduced.